The aim of the study is to formulate and evaluate enteric coated tablets using Isoxsuprine Hydrochloride as a model drug. Different core tablets and enteric coated tablets were prepared and drug release was studied. Isoxsuprine Hydrochloride core tablets were prepared by wet granulation method, using polymers, by changing drug ratios. The granules are evaluated for physical properties and the in-vitro drug release studies. Enteric coating was carried out using different sub coating materials. Enteric coating was performed in a mini coating pan at 107 rpm using low-pressure air atomized liquid spray technique. By changing the coating material, were done single coated, Double coated tablets are evaluated for uniformity hardness, friability, invitro disintegration and dissolution studies. The in-vitro drug release data was fitted into various kinetic models. All the formulations showed the values within the prescribed limit. It was observed that the higher rate and drug release was observed for the double coated tablets, this is because second layer having high viscosity.

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Formulation and Drug Release of Isoxsuprine
HCL Enteric Coated Tablets
V. Nagamani
Department of chemical Technology, Osmania University, Hyderabad, India
Abstract— The aim of the study is to formulate and
evaluate enteric coated tablets using Isoxsuprine
Hydrochloride as a model drug. Different core tablets and
enteric coated tablets were prepared and drug release was
studied. Isoxsuprine Hydrochloride core tablets were
prepared by wet granulation method, using polymers, by
changing drug ratios. The granules are evaluated for
physical properties and the in-vitro drug release studies.
Enteric coating was carried out using different sub coating
materials. Enteric coating was performed in a mini coating
pan at 107 rpm using low-pressure air atomized liquid
spray technique. By changing the coating material, were
done single coated, Double coated tablets are evaluated for
uniformity hardness, friability, invitro disintegration and
dissolution studies. The in-vitro drug release data was fitted
into various kinetic models. All the formulations showed the
values within the prescribed limit. It was observed that the
higher rate and drug release was observed for the double
coated tablets, this is because second layer having high
viscosity.
Keyword— Double coated tablets, disintegration and
dissolution studies, Enteric coated tablets, formulations,
Isoxsuprine Hydrochloride.
I. INTRODUCTION
Oral route of administration has been received more
attention in the pharmaceutical field because of the more
flexibility in the designing of dosage form than drug
delivery design for other routes. Most of the oral controlled
drug delivery systems rely on diffusion, dissolution or
combination of both mechanisms, to release the drug in a
controlled manner to the Gastrointestinal Tract (GIT) and
the drug profile data, such as dose, absorption properties
and the quantity of drug needed, one can determine the
desired release rate of the drug from1
controlled release
dosage form. Drugs that are easily absorbed from the G.I.T
and having a short half-life are eliminated quickly from the
blood circulation. To avoid this problem the oral controlled
release formulations have been developed, as these will
release the drug slowly into the GIT and maintain a constant
drug concentration in the serum for a longer period of
time.Isoxsuprine, or Isoxsuprine hydrochloride, is a drug
used as a vasodilator in humans and equines. Isoxsuprine is
most commonly used to treat hoof-related problems in the
horse.
Most commonly for laminitis and nonvascular disease, as
its effects as a vasodilator are thought to increase
circulation within the hoof to help counteract the problems
associated with these conditions. Enteric coatings are those,
which remain intact in the stomach, but they dissolve and
release the contents once it reaches small intestine. Their
prime intension is to delay the release of drugs, drugs
sensitive to the stomach contents or may cause nausea or
bleeding by irritation of gastric mucosa. There are three
reasons for putting such a coating on a tablet or capsule
Ingredient to protect the stomach, to protect the drug from
the stomach To release the drug after the stomach e.g. in the
intestines. The drugs which most commonly cause stomach
ulcers like aspirin, diclofenac and naproxen are frequently
available with enteric coatings. Omeprazole, which is a
drug which stops the stomach from producing acid, is itself
broken down in acid and therefore the drug generally has an
enteric coating around it either as a granule in the capsules
or as a granule in the dispersible form. Sulfasalazine is used
either for the treatment of arthritis or for the treatment of
Corn’s disease which is inflammation of the intestines.
When used for arthritis it is very often given without an
enteric coating so that it can be absorbed more quickly,
whereas for Crowns’ where it is needed in the intestines to
work it is given with an enteric coating. It can be seen that
an enteric coating is therefore there usually for a good
reason and therefore such tablets or the contents of enteric
coated capsules should never be crushed before being taken.
To formulate and evaluate the Enteric coated tablets using
Isoxsuprine Hydrochloride as a model drug by using
different polymers, to evaluate the granules prepared from
isoxsuprine Hcl for: Bulk density, Tapped density.
Hausners ratio and cars index, to evaluate the prepared
enteric coated tablets for: physical properties,Invitro drug
release studies, Drug release mechanism2
.3
.

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II. MATERIALS AND METHODS
Table.1: Selected excipients for formulations
S.no
Name of the
Ingredients
Category
1 Crosspovidone Disintegrating agent
2
Crasscarmellos
Sodium
Disintegrating agent
3 HPMC E15 Disintegrating agent
4 Carbapol Disintegrating agent
5 PVPK30 Binder
6
Sodium
carbonate
Alkalizing agent
7 Mannitol Diluent
8
Magnesium
Stearate
Lubricant
9 Talc Glidant
10 Isopropyl alcohol Solvent
Preparation of core tablets 4,5
:
The core tablets were prepared by wet granulation method.
All the ingredients (show in Table 1), were mixed and
passed through sieve no. 40 to get uniformally distributed
and uniform sized particles. These granules are compressed
on a single punching tablet machine. One batch of 20
tablets were prepared.
Preparation of enteric coated tablets:
The prepared core tablets were taken, for a single 2
coating
process. It has two coatings, coated with cellulose acetate
phthalate and HPMC .Required quantity of coating
materials were added slowly to the vortex zone and the
suspensions was mixed for 1hr.45 min.for single coated
tablets and for double coated tablets was maintained
without air bubbles then use the solution was used for
coating4
. The tablets were placed in a coating pan till the
average weight as per the specifications (given in table 3).
Table.2: Selected Enteric Coated Materials
S.no Name of ingredients Category
Sub coating
1 HPMC
Sub
coating
materials
2 Cellulose acetate phthalate
Sub
coating
materials
3 Isopropyl alcohol Solvent
Enteric coating
4 Meth acrylic acid
Enteric
coating
material
5 Titanium di oxide
Coloring
agent
Table.3: Specifications of Sub coating
Inlet temp(o
c) 60-65
Out let temp(o
c) 40-45
Spray gun rpm 2-3
Air pressure(kg/cm2
) 4-5
Analytical method /Standard calibration of curve of
Isoxsuprine
Hcl (pure drug) in suitable solvent
Fig.1: UV scanning image of pure Isoxsuprine hcl drug in
solvent chloroform
Calibration curve for Isoxsuprine Hcl drug:
y = 0.0289x
R2
= 0.999
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 5 10 15 20 25 30
Concentration
G/ml
A
b
s
o
r
b
a
n
c
e

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Cumulative analysis of Granules:
Table.4: Particle size of Granules
Granulates
(wt%)
Mean
thickness(µm)
Diameter of
granules(µm)
Particle
Size(µm)
3.0 52 30 0.0128
6.0 61 30 0.0226
9.0 75 30 0.0351
12.o 102 40 0.0425
15.o 110 40 0.0565
18.0 123 40 0.0638
Total
weight=21.0
123 30 0.0772
Table.5: Pre compression properties of uncoated tablets
S.n
o
Formulati
on code
Bulk
density
Tapped
density
Carr’s
index (%)
Hauser
’s ratio
(%)
1 F1 0.472 0.509 7.27 1.079
2 F2 0.374 0.398 6.03 1.064
3 F3 0.398 0.425 6.26 1.066
4 F4 0.404 0.432 6.48 1.069
5 F5 0.472 0.509 7.27 1.079
6 F6 0.447 0.481 7.07 1.075
Table. 6: Post compression properties of Isoxsuprine Hcl
uncoated tablets:
S.n
o
Formul
ation
code
Thick
ness
(mm)
Diamet
er
(mm)
Hardn
ess(k
g/cm2
)
Friabi
lity
(%)
Weig
ht
variat
ion
(mg)
1 F1
4.0±0.
03
9.0 4.4 0.623
393±
0.25
2 F2
3.9±0.
04
9.0 4.1 0.716
398±
0.30
3 F3
3.9±0.
05
9.0 4.6 0.657
397±
0.28
4 F4
4.0±0.
04
9.0 4.4 0.701
398±
0.04
5 F5
3.8±0.
06
9.0 4.3 0.664
396±
0.32
6 F6
3.8±0.
07
9.0 4.2 0.622
401±
0.16
Table.7: Post compression properties of Isoxsuprine Hcl
single coated tablets:
S.n
o
Formu
lation
code
Thickness
(mm)
Diameter
(mm)
Hardness
(Kg/cm2
)
Friability
test
1 Fs 4.8±0.03 9.5 4.9 0.697
2 Fs 5.0±0.04 9.5 4.8 0.724
3 Fs 4.9±0.05 9.5 5.1 0.65
4 Fs 5.0±0.04 9.5 4.9 0.73
5 Fs 4.8±0.06 9.5 5.2 0.85
6 Fs 5.0±0.07 9.5 4.8 0.80
7 Fs 4.9±0.02 9.5 4.9 0.83
8 Fs 5.0±0.03 9.5 5.0 0.82
Table.8: Post compression properties of Isoxsuprine Hcl
double coated tablets:
S.no
Formul
ation
code
Thickness
(mm)
Diameter
(mm)
Hardness
(Kg/cm2
)
Friability
test
1 Fd 5±0.03 10.0 5.2 0.85
2 Fd 5.5±0.05 10.0 5.4 0.76
3 Fd 5.4±0.05 10.0 5.2 0.89
4 Fd 5.5±0.06 10.0 5.2 0.91
5 Fd 5.3±0.03 10.0 5.5 0.88
6 Fd 5.3±0.04 10.0 5.4 0.86
7 Fd 5.5±0.04 10.0 5.3 0.88
8 Fd 5.4±0.03 10.0 5.4 0.92
Table.9: In vitro studies of Isoxsuprine Hcl uncoated tablets
Ti
me
Cumulati
ve drug
release
(%)F1
Cumula
tive
drug
release
(%) F2
Cumu
ltive
drug
releas
e(%)
F3
Cumu
ltive
drug
releas
e(%)F
4
Cumul
tive
drug
releas
e(%)F
5
Cumu
ltive
drug
releas
e(%)F
6
0 0 0 0 0 0 0
30 9.9 7.1 8.1 10.25 7.65 8.21
60 12.5 11.6 14.0 16.6 15.3 16.25
90 15.8 16.5 19.5 23.8 33.3 20.25
120 18.4 19.8 25.3 31.9 42.3 27.9
150 22.8 25.3 29.7 47.05 39.06 38.3
180 27.1 32.5 36.04 49.6 42.7 43.8
210 35.4 38.2 39.6 54.8 50.85 49.4
240 47.89 47.1 45.0 59.03 54.8 56.92
270 58.99 57.5 58.2 61.8 59.6 58.2
300 62.8 65.3 64.05 68.04 61.5 63.7

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330 69.3 69.6 66.3 70.25 65.9 63.7
360 72.57 76.5 76.7 75.6 71.3 69.9
390 78.4 79.01 79.0 79.21 75.8 73.1
420 85.2 85 83.5 81.3 77.2 75.9
450 89.6 89.9 85.2 84.5 79.6 79.8
480 94.5 93.4 88.9 85.3 80.6 81.5
In vivo drug release for all formulations:
Drug release of enteric coated tablets:
Table.10: Invitro drug release of single coated tablets
Time
( min)
Cumulative
drug
release
(%)Fs
Cumulative
drug release
(%)Fs
Cumulative
drug release
(%)Fs
Cumul
ative
drug
release
(%)Fs
0 0 0 0 0
30 15.7 14.8 15.8 18.6
60 29.8 30.6 25.9 29.3
90 35.6 34.8 38.2 39.5
120 48.2 49.6 47.8 49.6
150 55.6 55.7 59.5 55.7
180 79.6 69.8 66.6 68.2
210 75.2 79.8 73.2 77.8
240 81.2 84.3 78.4 79.1
270 85.4 88.6 81.4 84.5
300 89.2 89.2 83.2 91.1
330 94.5 92.4 93.5 92.3
Table.11: Double coated tablets
Time(mi
n)
Cumulati
ve drug
release Fd
Cumulati
ve drug
release Fd
Cumulati
ve drug
releaseFd
Cumulati
ve drug
releaseFd
0 0 0 0 0
30 28.6 29.8 34.8 36.9
60 41.5 45.9 45.9 48.4
90 58.4 57.3 51.6 53.4
120 63.5 67.8 59.4 58.9
150 83.4 71.3 69.7 59.8
180 88.9 79.3 78.7 63.8
210 92 81.3 79 63.8
240 93.2 86.8 80.6 79
270 94.8 89.8 82.4 82.1
300 94.8 92.6 85.3 90.5
330 95.8 94.5 86.9 92.3
Table.12:The invitro disintegration studies for coated
tablets
S.no Single coated
tablets
Disintegrating time
1 FS11 3hrs
2 FS12 2hr.30min
3 FS21 2hrs
4 FS22 2hr.30min
0
50
100
0 200 400 600
Cumulativedrug
release(%)
Time
F1
F2
F3
F4
F5
0
50
100
0 100 200 300 400
Cumulativedrug
release(%)
Time
Single coated tablets
F11
F12
F22
0
50
100
150
0 200 400
Cumulativedrug
release(%)
Time
Double coated tablets
F11
F12
F21
F22

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Table.13: Double coated tablets
S.no Double coated
tablets
Disintegrating time
1 Fd11 2hrs
2 Fd12 1.30min
3 Fd21 2hrs
4 Fd22 2hrs
III. CONCLUSIONS
From the present study we conclude that, amongst the all
polymers studied,HPMC has shown has shown best drug
release. Of the two coatings i.e. single coated, double
coated tablets as shown best drug release. From the
Disintegration and dissolution studies, it is observed that,
in double coated tablets, drug will release faster than other
coatings because the second layer is made up of high
viscosity material.(because of coat thickness 5.5±0.05 and
viscosity 4000cps).All the formulations are satisfactory
with a proper disintegration time. In the case of uncoated
tablets drug release is slower, where as in coated tablets
drug release is observed to be faster. Enteric coated tablets
are easily dissolved in the dissolution apparatus(it is at
pH 6.8),hence will dissolve in Gastro intestinal tract
which is also at pH 6.8.For Isoxsuprine hydrochloride
coating is necessary, as it makes the unpleasant taste and
gives a smooth finish.
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